Battery Question

[webley445]

Hope this is the right section for posting. It is not about batteries in flashlights though. I figured if there was any place I could get bayyery questions answered it would be on CPF.

I recently got a ham radio license and bought a handheld radio. This unit has a factory made Nicad battery rated at 700 mAh. It is basically a sealed plastic case that holds 6 AA Nicads and is charged with a AC power supply.

There is an accessory that is a battery pack that opens up and accepts AA alkalines or Nihms. I'm wondering about an estimate on how much more run time would I be able to get buy running 6 rechargeables in the 2100mAh range. Anyone willing to take a guess?

Currently I'm able to get 3-4 days of use out of the radio if I am careful about my useage and keep things to a minimum.
What I'm looking for not having to worry about how much I use the radio and being able to recharge the battery pack in a few hours instead of overnight as I currently do with the NiCads. Plus there is the issue of battery memory (a problem we've had with NiCads that are used at my job).
Will appreciate any advice.

 

[Niconical]

To answer your principle question, how much more runtime will I get? The answer is lots.

If you have a device that can take 6xNimh (we'll skip alkaline) instead of the battery pack, then go for it.

1 of these will be fine
1 of these if you'd rather go 'pro' with it
3 packs of these (12 total, 6 in, 6 waiting)


Job done, you won't look back

 

[Marduke]

5-6 times more runtime.

 

[Mr Happy]

5-6 times more runtime.

Well hang on...if you go from 700 mAh to 2100 mAh isn't that going to be 3x more run time?

On the other hand, if you can open up the battery pack and replace the flat batteries with fresh ones, the only limit is how many spares you want to have around. And the great thing of course is you can have spare eneloops charged and waiting so you can do an instant swap when the current set runs out.

 

[Marduke]

Well hang on...if you go from 700 mAh to 2100 mAh isn't that going to be 3x more run time?

On the other hand, if you can open up the battery pack and replace the flat batteries with fresh ones, the only limit is how many spares you want to have around. And the great thing of course is you can have spare eneloops charged and waiting so you can do an instant swap when the current set runs out.

Most AA NiCad's I've seen are 400-500, not 700.

 

[mdocod]

Sounds like a perfect application for LSD AA cells.

I would be willing to bet that while on paper, there is only a 3X increase in runtime, in reality, there will very likely be a 4-7+X increase in runtime as a result of the LSD cells holding a charge through the days/weeks of service much better than the NiCD cells. In many low drain applications, a worn out nickel chemistry cell will actually self discharge at a faster rate than the consumption of the device...

-Eric

 

[vali]

Most AA NiCad's I've seen are 400-500, not 700.

I only have 3 NiCads left.

One of them, Tronic brand, is rated at 600 mAh. It was used moderately but charged without care in a timed charger. After break-in and a 5 charge/discharge cycles in my C9000 the capacity is 500 mAh.

The other 2 are carrefour. I bought them around year 2000 (IIRC), were charged once and forgotten in a cheapy flashlight. I found them a couple of months ago and did the same procedure as the Tronic one. They are rated at 700 mAh and I got 804 mAh and 808 mAh. I allways thought supermarket brands had less than stated capacity, but these seems to be an oddity.

 

[lumenosity]

Sounds like a perfect application for LSD AA cells.

+1 on the Low Self Discharge AA's...

I've been using some Rayovac Hybrid AA's in my handheld ham radio for a year or 2 now. Before with nicads, if I didn't use the radio for awhile, I'd have to charge the battery first. With the LSD batteries, it can sit for months and the battery still has a good charge... better for emergencies and less hassle too

 

[webley445]

Thanks for the replies.

I looked at the current battery pack and I'm not sure if I can get it apart without damaging it, and not sure if nihm AA's will fit properly. Holding the replacement AA's up to the pack, it appears they are a tad longer, and I have experienced slight differences in length/diameter in batteries.

From more researching I have found lith battery packs available for the unit in 1400-1800 mAh range that use drop in chargers that are stated to charge the packs in 3-4 hours. Cost would be about the same as getting all set up with battery carrier, new LSD AA's, and charger. So now there are more options to weigh.

lumenosity,
being your experienced with ham radios which do you think is better?

 

[lumenosity]

each has its pros and cons...

If the lithium pack has a higher voltage, it may allow your radio to transmit on "high power" (depending on the radio). If this is the case, then a lithium pack is the better option. The full 5 watts does make a difference and helps you "get out" farther. Also the drop-in charger is convenient if you plan on using the radio a lot.

If the radio will still transmit on full power with the AA's, then the AA's are a good option as well. Benefits of AA is you then have the charger to do other things with. Also if you plan on buying multiple packs, AA's will be cheaper because 6 AA's is probably cheaper than a single Lithium pack. Nice thing is you can always use akalines in an emergency if needed.

I'd definitely go the "high power" route first, but if there is no difference the AA's are an attractive option.

 

[mdocod]

Holding the replacement AA's up to the pack, it appears they are a tad longer, and I have experienced slight differences in length/diameter in batteries.

I'm not sure how much of a difference in length you are seeing there.. In some cases, it may just be that you are seeing the difference of the button top compared to a flat top cell. In other cases, it's possible that they are actually a shorter cell. There is such a thing as a 4/5AA cell and they are commonly found in pack applications. They are usually ~43mm actual length, compared to the 50mm of a standard AA cell.